1. Field of the Invention
The present invention relates to diagnostic and therapeutic nanoparticles. More particularly, the present invention relates to creating a copper (Cu)-based nanoparticle and a method for making the same. The Cu-based nanoparticles can further be incorporated with additional therapeutic or diagnostic agents. The nanoparticles of the present invention have the capability to absorb near infrared wavelength light to act as a therapeutic agent by generating heat energy effective for cell ablation.
2. Description of the Prior Art
Cancer is a group of diseases characterized by uncontrolled growth and spread of abnormal cells. If the spread is not controlled, it can result in death. Cancer is caused by both external factors (tobacco, infectious organisms, chemicals, and radiation) and internal factors (inherited mutations, hormones, immune conditions, and mutations that occur from metabolism). Cancer is treated with surgery, radiation, chemotherapy, hormone therapy, biological therapy, and targeted therapy. In 2011, about 571,950 Americans are expected to die of cancer, more than 1,500 people a day. Cancer is the second most common cause of death in the US, exceeded only by heart disease. In the US, cancer accounts for nearly 1 of every 4 deaths. (Cancer Facts and Figures 2011, American Cancer Society).
Cancer of the liver affects greater than half a million patients worldwide. U.S. liver-related cancer deaths account for 4% of all cancers or about 20,000 deaths annually. Currently available minimally invasive procedures have the tendency to leave a population of malignant cells intact, allowing for recurrence of the tumor and accounts for the varied recurrence rates seen.
Similarly, the rate of prostate cancer in men was 33% of all cancers in the U.S. in 2004. Prostate cancer easily metastasizes, increasing the chance of death if not caught early. In the current stage of detection through prostate specific antigen (PSA), at least 25% of U.S. men tested as present with metastases to the bone. These men have a 90% risk of death within five years. The high mortality rates of these cancers after metastasis, is a significant health risk.
Nanoparticles can be efficiently delivered into cancerous tissue, such as tumors, via a property inherent of fast growing neoplasias called Enhanced Permeability and Retention (“EPR”). This property is marked by “leaky vasculature” within tumors, allowing extravasation and retention of macromolecules or nanoscale particles. Silica core/gold nanoshells (composite nanoparticles) which have tunable plasmon resonance in the near infrared (“NIR”) range have been used to induce sufficient thermal damage after accumulation via this mechanism leading to tumor reduction and increased survival. Using light based imaging techniques (optical coherence tomography or OCT) these nanoparticles have been used as a theranostic (i.e., combined diagnostic and therapeutic) agent in a single nanoshell formulation. Though these particles may provide effective diagnostic capabilities for shallow (<5 mm) tumors they are unsuitable as a good diagnostic approach where tumors may be deeply situated.
However, in addition to being expensive, the size of the gold nanoparticles smaller than 10 nm are not easy to make. Special structures like core-shell nanostructures and hollow gold nanorods are required in order for gold nanostructures to have absorption in the NIR ranges, and the recipes for making these nanostructures are very complicated. Thus, a need exists for a therapeutic agent having strong absorption in the NIR region, small size, low cost of production relative to gold particles, and low cytotoxicity.
Photothermic Ablation (PTA) of cancer is the use of heat between 41° C. and 45° C. to damage cancer cells. PTA is an effective modality for cancer treatment that has been investigated extensively. The beauty of PTA is its duality for targeting—that is the targeting of the agents and the light that used for activation. The duality of targeting can effectively reduce the side effects and the risk of damage to the surrounding healthy tissue. A significant obstacle to successful PTA is that healthy tissues can also absorb energies and could be damaged by heat. The application of functional nanoparticles may overcome this limitation because nanoparticles can be selectively directed to the cancer cells. Gold nanostructures (nanoparticles, nanoshells, and hollow nanospheres) have been investigated extensively for photothermal ablation therapy induced by NIR light, hence the term photothermal ablation therapy. As a new type of agents for photothermal treatment of cancer, CuS nanoparticles have many advantages. The most favorable features are the low-costs, simple and easy for preparation and small size for targeting.